LMAO - okay so I am a tard - the first time I forgot to tip the occ driver - um it was 4 AM!!!!!!  And he STILL PICKED us up - then I was so tired I forgot to tip him...so the next time I saw him I gave him $20 to make up for my stupidness 
I usually tip $5 - just cuz then they seem to take care of me lol. 
I even do that when we go out for the first few drinks - and seriously we are treated like queens for everything.  I know lots of people only give a dollar or two though.  For waiters - I tip more if they are good...the better they are the more I tip - I used to be in service and I definately try to tip well since I can afford to...they really dont make a lot. 
My friend is a waiter at a bar in TJ.  He gets paid $20 a shift.  Thats it.  THEN - at the end of the night he has to take money from that $20 and whatever tips he gets.  He has to give something like $6 to the DJ, $5 to the manager, $5 to the bartender and $5 to someone else (I cant remember)...some nights, he takes NOTHING home.  They get paid crap - so I keep that in mind.  Seeing as most of us make more in 1 hour than they do in an entire day - I like to surprise some of them